The frit fly (FF),Oscinella frit(L.), is a pest of golf course and home lawn turfgrasses. Adult occurrence was monitored with a sweep net and a modified unit area sweep net. There are three and a partial fourth generations per year in northern Ohio (Wooster). Adult peak densities occurred during mid-May, late June, late July-early August, and mid-September in 1984. FF adult peaks were about 2 wk earlier in 1985. There was a slight male bias in sex ratios within sampling nets because of sampling technique and FF behavior. Parous females were determined by examining ovarian morphology. Parasitic nematodes were found within FF abdomens. Five of eight FF adult occurrence periods indicated major ovipositional activity when 40% of adults occurred (approximate time of control treatment). The best linear regression models for predicting 40% adult occurrence were a base temperature of 0°C and a 1 March starting date. Degree-day prediction methods may be more reliable for targeting dates to time control programs than calendar dates.